ARC~USA offers many different elastomeric-type connectors and can supply whatever the customer needs if the application is fully explained. since all elastomeric connectors are "custom made", this guide provides the reader with a clear understanding regarding:
- The range of elastomeric connector configurations.
- Customer information needed for ARC to effectively develop an elastomeric connector for specific applications.
- A customer checklist important to the design and development of elastomeric connectors.
- The general characteristics of elastomeric connectors.
Connector type - (G)
FeaturesThese connectors are used in designs where side insulation is not required or where a wider conductive path is needed than the 0.4mm common with the (GL) styles. These connectors range in width from a minimum of 0.25mm (0.010") to a maximum of 1.4mm (0.055"). If the desired width exceeds 1.4mm (0.055"), (GL) style connectors should always be recommended.
Connector Type - (G2)
FeaturesThe (G2) is a thin version of the (G) connector and is used when the space available to work with is extremely narrow, but side insulation is required. This connector has a special, thin side insulation applied that shields it from metallic casing if this casing is used in customer's application The thickness of the side insulation is limited to </- 0.05mm, and cannot be applied more thinly or thickly, so great care must be taken when recommending this connector to avoid alignment problems. These connectors range in width from 0.25mm (0.010") to 1.4mm (0.055").
Connector Type - (GL)
FeaturesThis connector consists of alternating layers of conductive and non-conductive material sand wiched between outside layers of soft, non-conductive insulating material. The minimum width of (GL) connectors is 1.4mm (0.055"). If a narrower connector is required, the customer must select from the (G) and (G2) styles. (GL) connectors can be "color coded" (insulative material on one side colored red, green, etc.) if the insulating layers are not the same width. This color coding is done so the customer can use the connector in his product without worrying whether or not is has been assembled (inserted) properly. Color coding is also often used to solve alignment problems
Connector Type - (GL-A)
FeaturesThis connector is simply a double-row (GL) connector with insulating material between the two (2) rows of conductive material and on the outside walls of the connector. (GL-A) connectors provide two (2) rows of contacts for applications when electrodes on the surfaces to be joined are not in a single straight line.
Connector Type - (GS)
Connector Type -FCL
FeaturesThis connector is used for right-angle connections between LCD's and printed circuit boards. All FCL connectors require tooling charges as there are no standard sizes available. Tooling charges range from $2,500 to $6,000. Since samples of FCL connectors are "hand made" and very costly, lot charges are usually required. Contact ARC for lot charges and lead times.
Connector Type -FK
FeaturesThis connector is used to make connections on the common side of LCD's - connecting electrodes on the top surface of the LCD to the printed circuit board. This connector fully insulates the LCD from mounting grounds because it is completely covered with insulating material and can only make contact with the PCS through it's narrow (channel) conductive area. Almost all FK connectors require tooling charges. There are a few standard sizes available, but the selection is very, very small. Tooling charges for FK connectors are around $5,000.
Elastomeric Connector Design Requirements
All elastomeric connectors are "custom made", and ARC requires the following information in order to successfully quote and supply against all inquiries received:LENGTH (L): WIDTH Width PITCH
:
Shaded Portion is Conductive Material - Unshaded Portion is Nonconductive Material
HEIGHT (H):
A connector's Height (H) is important because it is used to calculate the correct compression (deflection rate) to be applied to the connector for reliable connections.The typical compression (deflection rate) to be applied to connectors varies with the type (G, G2, GL). The rates below are recommended by ARC for most applications. Connectors G, G2, and GL types. If H is less than 6mm: 15% of connector's height. If H is more than 6mm but less than 10mm: 13% of connector's height. If H is more than 10mm: 10% of connector's height.
WIDTH (W):
Width (W) is important because it's design is critical in eliminating buckling when clamping force is applied to the connector. If a connector buckles, it's resistance rises. If the buckling is too severe, contact can be lost completely.ARC strongly recommends that the ratio between the H and W of a connector be as close to one-to-one as possible. In other words, the connector should be as close to "square" as possible. Although the H of the connector can be as small as 1/4W, it is recommended that the H not be less than 3/4W. Most ARC connectors (particularly G and G2 types which are very thin and have a thin insulating coating) require plastic holders ("pockets") of some type to facilitate assembly, prevent accidental side contact and eliminate alignment problems.
width (w):
Conductive width (w) is important because it is instrumental in determining the cost, resistance and rigidity of the connector.The more conductive material a connector contains, the more expensive it is. Therefore, it is very important to keep the conductive layer as narrow (small) as possible when cost is the overriding concern in a product's design. In addition to keeping the conductive layer as narrow as possible, it should also be kept within ARC's standard sizes whenever possible. ARC's standard dimension for the conductive layer width is 0.4mm. (Consult ARC's catalog for the standard individual conductor widths available) The conductive layer (w) should not only be as narrow as possible, but the Pitch (P) should be as wide (far apart) as possible to keep cost to a minimum. ARC also offers many non-conductive materials for insulating it's connectors. These non-conductive materials are rated according to hardness so the correct load compression (deflection rate) is calculated for reliable interconnections.
LENGTH (L):
Length (L) is important only in that it must fit the customer's particular application. This is very important when the connector is being fitted into some type of plastic holder.Tolerances for elastomeric connectors can be found in ARC's connector/keypad catalog with the maximum length being 300mm +/- 1.0mm (11.82" +/- .04").
PITCH (P):
Pitch (P) is important because it guarantees a reliable connection is made between the two (2) surfaces being joined.ARC recommends three (3) conductors per electrode, although two (2) is often adequate to ensure all connections are reliable and to eliminate "intermittent contact". In order to minimize cost, it is strongly recommended that customers utilize ARC's standard pitches in their connector designs whenever possible. The following tables illustrate the number of conductors per inch in each of ARC's standard connectors. The second table lists pitch recommendations.
TABLE 1
PITCH (P) (MM) Conductors Per Inch PITCH (P) (IN)
0.40 63 .016"
0.25 100 0.10"
0.18 143 .007"
0.15 170 .006"
0.10 254 .004"
TABLE 11
Electrode/Pad Spacing/3 = (in/mm) Recommended Connector Pitch (mm)
.040"/1.0 0.25
.030"/0.76 0.25
.020"/0.508 0.18
.015"/0.380 0.15
.010"/0.254 0.10
EXTRA FINE ITCH (P):
The extra fine pitch allows enhanced connectivity in LCD/PCB assembly. The finer pitch will allow more conductive traces per electrode on these two devices for surer connections. The increased number of conductive traces per electrode also allows for lower ohm values.
Extra Fine Pitch Dimensional Tolerances in MM
Pitch Length Height Width Core-width Conductor-width Insulator-width
0.05+/-0.03 2.0---25+/-0.2 1.0---3.0+/-0.1 1.0---2.5+/-0.1 0.4+/-0.05 0.025+/-0.02 0.025+/-0/02
25.1---50+/-0.3 3.1---5.0+/-0.15 2.6---5.0+/-0.15 0.7+/-0.05
50.1---80+/-0.4 5.01---10.0+/-0.2
80.1---120+/-0.5 10.0&up+/-0.2
120.1---150+/-0.6
150.1---200+/-0.8
200.1&up+/-1.0
The following provides the customer with a checklist that should be reviewed when connectors are going to be used.The cost of a connector is directly linked to the amount of conductive material it contains. Elastomeric connectors usually require bezels of some type to promote easy assembly and eliminate alignment problems. Bezels, or holders, are also used with elastomeric connectors to prevent over compression of the connector and buckling problems. The more "square" (H x W: 1 to 1 ) a connector is, the more likely it will not require a bezel, or holder, when assembled. Connectors can be color-coded for easy identification when side insulation is not identical on both sides of the connector. Elastomeric connectors utilizing carbon conductors are much cheaper than those using silver.. In addition, carbon connectors remain oxidation-free over the life of the connector. The conductive areas of elastomeric connectors should never be handled by human hands because the oils and contaminants inherent in the human body can cause contact problems after the product is assembled. High-quality connectors can only be supplied if the manufacturing process in completely sanitary and the raw materials utilized are of exceptional quality. ARC connectors go through two (2) curing - the second being six (6) hours at 200ºC. The second curing is critical because it eliminates siloxanes which cause contact problems as connectors are left out in the field. The most popular connector currently being used in the United States is the (GL) style. (GL) style connectors, with a pitch of 0.25, are suitable for most LCD applications. ARC's FK and FCL-type elastomeric connectors require tooling charges. Although samples can be made by hand, production orders cannot. ARC can manufacture almost any type of connector if complete design information is supplied. If the dimensions of a connector are not known, the pitch for the same can be determined by obtaining the dimensions for the pads on the printed circuit board. The height of the connector can be determined by finding the distance between the LCD and the printed circuit board, then adjusting for connector deflection (approximately 15%).
Physical and Electrical Properties of Elastomeric Connectors
The following table provides a summary of the physical and electrical properties of elastomeric connectors.
Volume Resistivity: standard 5.0 cm²
Operating Temperature -20ºC to +180ºC
Storage Temperature -20ºC to +180ºC
Dielectric Strength 25 kv/mm
Insulative Resistance @ 500 VDC 10¹² ohms
Current Carrying Capacity: standard 1 mA/mm²
Conductive Layers Per Inch:standard .25-.10mm More than100, but less than 500
Deflection: connectors using carbon conductors 10% to 15%
Skew Less than 1.5
Compression Height The following formula can be used to determine the uncompressed height of the connector to be ordered, when the compressed height (space between LCD and PCB in assembly) and the percentage of compression are known but the height prior to assembly is not certain. x = uncompressed height, n = compressed height, % = percent of desired compression
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